Lubricant



Patented Oct. 25, 1938 UNITED. STATES KGTBTGHCB 2,134,432 PATENT ()FFlCE,

2,134,432 LUBRICANT sylvania No Drawing.

Application August 31, 1936,

Serial No. 98,826

7 Claims.

This invention relates to improved lubricants andprocesses of making the same; and it comprises lubricating compositions and lubricants containing small amounts of improvement agents which mitigrate or retard the normal destructive action of lubricating oil deterioration products on certain bearing surfaces, the improvement in this respect being noteworthy with even such bearing materials as alloys of cadmium with silver and copper, of cadmium with nickel and of lead with copper and nickel, etc., even under relatively high temperatures, speeds and pressures, this improvement of the mineral oil being effected and its performance improved by the presence therein of a small amount of an alkyl thioether of orthonitrobenzene; and it also comprises methods of making an improved oil wherein such orthonitrophenyl alkyl, thioether is incorporated in the oil prior to application of the lubricant to a bearing; all as more fully hereinafter set forth and as claimed.

Recent developments in the design of mechanical equipment for generating and transmitting power, and particularly .in the automotive field, have necessitated new bearing metals with special properties. Among these new bearings are binary and ternary alloys of the metals mentioned above. Cadmium-silver-copper, cadmium-nickel-copper, copper-le'ad-nickel, etc., alloys are in use. One ternary alloy currently used in automobile engines is an'alloy of. cadmium with minor amounts of both silver and copper. 'Under the conditions imposed by modern engineering design these new alloy bearings are commonly subjected to more severe operating conditions than were usual in the older art: to higher bearing loads, higher rubbing speeds and higher temperatures of operation. It

is found that in actual use under these conditions there often develops quite serious destructive action on the bearing surface by mineral lubricating oils, even by those standard commercial oils giving particularly good results with the older bearing metals under the earlier operating conditions. The destruction of the bearing metal probably results from action of deterioration products developed inthe oil. An object achieved in the present invention is the production of lubricating oils improved for these newer conditions of use and which are characterized by reduction or elimination of destructive action on the newer bearing metals by deterioration products in the oil.

We; ave discovered that the alkyl thioethers of orthorhtrobenzene, incorporated with lubricants, are capable of achieving the objects of the present invention, the alkyl thioethers, such as those confactorily lubricate alloy bearings. Incorporated in mineral oil, these thioethers retard destruction of the bearing metal. Also, the film strength of the lubricant is increased, the thioethers imparting extreme pressure characteristics to the oil. The character and amount of added improvement agents, here employed, are such that the normal physical properties of the oil, such as viscosity, gravity, color, etc., are not substantially altered. Certain properties of the lubricant are improved without-sacrificing the other desirable properties.

We obtain improved mineral oils and lubricants suitable for lubricating bearings under a wide range of service conditions. The new compounded lubricant satisfactorily lubricates the new alloy bearings even under high unit pressure, high bearing speeds and high operating temperatures. When prepared from suitable motor oils, the present improved compositions are excellent lubricants for the modern automobile engine. They satisfactorily lubricate the bearings without any destruction of the special bearing alloys now used, "even inthe presence of a free circulation of air.

Ordinarily between 0.05 and 0.50 per cent, by weight on the oil, of these thioethers is sufficient to produce a satisfactory lubricant. However, in some cases larger amounts of the thioethers may be employed, for instance, with those oils of more pronounced destructive tendency. As much as 1 per cent of thioether may sometimes be added with advantage. The particular proportions de pend upon the particular thioether and lubricating base employed and the particular type of lubricant desired.

When larger amounts are employed, extreme pressure characteristics are also imparted to the mineral oil or lubricant. In many cases, the load carrying capacity of the lubricant may be in-- QM NO:

wherein R represents an alkyl group. As a class, these thioethers are soluble and miscible with mineral oils in substantial proportions. We have found that they are sufficiently soluble and miscible to permit incorporation with the mineral oil of an amount of thioether suflicient to obtain the described improvement.

These thioethers may be readily prepared from a halogenated ortho-nitrobenzene and the metal oearcn HOOK salt of a suitable mercaptan such as the sodium salts of aliphatic mercaptans, the following equation illustrating the typical reaction wherein R represents an alkyl radical and M is a metal, advantageously an alkali metal.

In our copending'application Serial No. 98,828, filed August 31, 1936, we have described and claimed such new thioethers and methods of preparing and isolating them. One advantageous separately prepared by dissolving one mol of said chloro compound in asuitable volume of 95 per cent ethyl alcohol. The solutions so prepared are mixed and reacted under reflux until the reaction is substantially complete, usually 2 to 4 hours being required. The reaction being exothermic, the reaction mixture is controlled to conveniently dissipate the heat; refluxing of the solvent being advantageously utilized for this purpose. After the reaction is substantially complete the solution of thioether is filtered to remove the sodium chloride. Then the solvent is separated to recover the thioether.

The reaction product so obtained may be employed in the present invention. If desired the thioether may be further'purifled by recrystallization, washing with water and the other methods described in Serial No. 98,828, before incorporating it in the lubricating base in the practice of this invention. Likewise, thioethers prepared by other methods may be here employed.

As stated ante, thioethers containing alkyl groups, such as the various amyl groups, are particularly efiective for the present purposes. All the amyl groups give good materials for the present purposes. Of these, the normal amyl thioether of ortho-nitrobenzene is typical; the amyl compound has the following formula QB-CIHH Commercial amyl preparations often contain all of the possible isomers and may be used in making mixed thioethers desirable for the present purposes. There are some specific advantages both in n-amyl and iso-amyl compositions. The same is true of the thioethers derived from the butyls and propyls: each has specific advantages in certain relations. Other alkyl thioethers which are advantageous for the present purposes are ortho-nitrophenyl-ethyl-thioether ortho-nltrophenyl-butyl-thioether ortho-nitrophenyl-propyl-thioether These specific thioethera'espeoially advantageous for improving petroleum oils and mineral oil lubricants, as sub-class, may be represented by the following formula Qscm-romo-om I N01 wherein a is 0 to 3. However, in the broad practice of this invention other thioethers of orthonitrobenzene may be employed.

These thioethers are quite stable, even at the I elevated operating temperatures usually encountered in the lubrication of alloy bearings. Also, they are substantially neutral in reaction. Most of them are liquids at normal temperatures, although some are solids melting at relatively low temperatures. Generally, their color varies from a pale yellow to a reddish yellow and when dissolved in the mineral oil, the color of the oil is only slightly altered. The amyl and ethyl thioethers are liquid; they being typical, some of their properties here important are given in the following table. The amyl thioether is made from a commercial amyl mercaptan and contains various amyl groups.

11: 4 nil Sulfur: Percent- Neutralization No- From the above table the variation in physical properties with the length and complexity of the aliphatic constitu nt of the thioether is generally indicated. By employing thioethers containing other alkyl groups these properties may be varied at will to obtain certain advantages in particular embodiments of the present invention. This may be readily done by selecting the desired mercaptan in making the thioether by the reactions described ante.

Generally, the thioethers here employed are readily miscible and compatible with petroleum oils in the percentages necessary for the present purposes. They may be incorporated with the mineral oil or lubricating base in any suitable manner. They may be dissolved in the oil by simply mixing'the thioether with the oil and slightly warming with agitation to obtain uniform lubricants. Warming to temperatures between 100 F. and 180 F. is usually sufiicient: the thioethers being readily soluble. With the heavier and more viscous lubricating oils this warming is advantageous since the heating lowers the viscosity of the oil facilitating the blending. In some cases, the thioethers may be dissolved in suitable volatile solvents and the solution added to the oil, the solventbeing subsequently distilled off. This solvent method is particularly effective with the solid thioethers. Also,

the thioethers may be first dissolved in a suit- I oil to give a range of lubricating compositions as desired. Likewise the compounded lubricant may be converted into thickened compositions or greases in any of the usual ways. Sometimes the thioether may be directly added to metal soap greases or other compounded lubricants in which a petroleum oil is the lubricating base.

In the practice of the present invention any suitable lubricating oil base may be employed, either heavy or light oil. Ordinarily it is best to select a good grade of lubricating oil which has suitable initial properties for the particular lubrication requirement. Then the addition of the thioether produces the additional desired characteristics of restraining their destructiveness toward the newer alloy bearing metals, etc.

-is subsequently-blended with more lubricating I 252. COMPOSiTlONS.

That is, petroleum oils and lubricants of the usual grades may be employed in practicing this invention. The oils falling within the well known S. A. E. classification are among those which can and quickly determine the destructive action of oil deterioration products on a standard, comparable and reproducible basis to readily evaluate commercial lubricants for such alloy bearings. We have devised a satisfactory accelerated test procedure which is as follows.

An alloy bearing shell of certain commonly used standard dimensions is submerged in 300 cc. of the oil or oil composition in a 400 cc. pyrex beaker and heated in a thermostatically controlled oil bath to 175 C. (347 F.) and air, at the rate of 2000 cc. per hour, is bubbled through the oil in contact with the bearing shell. At the end of 48 and- 96 hours, the loss of weight and the condition of the bearing shell are determined. In determining the loss in weight the bearing shell is washed'free of oil and dried before weighing. This test will hereinafter be referred to as our standard laboratory test. When determining the efiectiveness of various improvement agents the usual procedure is to run a blank" test simultaneously with the 011 composition being tested, employing for that purpose a sample of the untreated oil.

In such tests it is advantageous to employ commercial bearing shells. These shells comprise a suitable metal backing faced with the alloy bearing metal. In the above test, the air is bubbled against the alloy bearing face. In this way, the actual bearing face is subjected to severe deteriorative conditions. By comparison of the results of such tests with actual service tests, we have found them to be in substantial agreement as to the suitability of particular lubricants.

In testing our-lubricants, we have employed,-

among others, bearings of the following approximate composition:

Such alloys are used in the tests of illustrative improved lubricants given post. In such tests the loss in weight, while not extremely high when expressed as per cent loss", is nevertheless very significant, as the bearing shells used have an alloy facing of only .008 inch to .012 inch thickness on a highly resistant backing and the observed losses in the reported tests often represent a loss of the order of ten per cent of the alloy facing.

muse ilUlUlUIIbU The specific examples and tests given post are illustrative of detail embodiments of the present invention.

Example 1.Into a suitable vessel there were introduced 1000 gallons (approximately 7200 pounds) of Pennsylvania motor oil S. A. E. 10 grade and the oil was warmed to 160 F. Then 7.2 pounds of the amyl thioether of ortho-nitrobenzene (0.10 per cent by weight on the oil) was gradually added and the mixture agitated until a uniform blend was obtained; about 1 hour being required. In agitating the mixture, ordinary mechanical agitators may be employed or a current of air may be passed through the warm mixture to produce uniform blending. The amyl thioether used in this example had the properties given in Table A ante and was a mixture of isomeric amyl compounds, it being prepared from a commercial amyl mercaptan and from commercial ortho-nitrochlorobenzene, both of which are widely marketed in the chemical industries under those names.

The properties of the original and improved motor oil are as follows:

Table B Improved Original oil lubricant Gravity API Viscosity, SUV:

Neutralization No Copper strip test 0. i 0. 01 Satisfactory Satisfactory Improved Bearing shell, weight Grams -0. 4205 Substantial loss Badly etched and pitted Grams Beiore test. 27 51 Alter test Total change Comment Bearing appearance (alter test).

No change From the above results, the beneficial eifect of the thioether as annimprovement agent for the oil is quite apparent. This improved lubri-' cant, when tested in an automobile engine equipped with like bearings, was highly satisfactory and no destructive effect on the hearing was observed after a severe test run. Thus the standard laboratory test and actual service test gave similar results.

Example 2.Employing the same motor oil and blending procedure as in Example 1, 0.05 per cent by weightoi the same thioether was incorporated in the motor oil. The improved motor oil so obtained was likewise satisfactoryv for lubricating these alloy bearings without any No loss substantial destructive effect, although it contained only half as much of the thioether as in Example 1.

Table D Bearing shell,

Improved lubriweight Original oil cant Grams Grams Before test 27. 7925 27. 2258 Aiter test. 27. 3781 27. 2170 Total change -0. 4144 Comment Substantial loss Bearing ap ance Badly etched and pitted (after testi.

0. 0088 Insignificant loss N 0 change From the above results, it is clear that even a trace of thioether substantially improves the performance of the oil under service conditions. The improved lubricant of Example 2 when also subjected "to a service test in a modern automobile engine, gave good lubrication without any destructive action on the alloy bearings.

Example 3.Employing the procedure of Example 1, 0.5 part by weight of the amyl thioether of ortho-nitrobenzene was incorporated in a solvent refined Mid-Continent motor oil of S.A.E. 20 grade. The properties of the original oil and the improved lubricant so obtained from it were as follows:

4 Table E Improved Original oil lubricant Gravity: API 28.3 28.2 Viscosity, SUV:

. Percent 0 Neutralization N 0...- 0. to

0.02 Copper strip test Batisiac ry Satisfactory Again it is apparent from the above table that the addition of the thioether does not materially change the commonly determined physical properties of the 011. However, the performance of the oil was markedly improved. The increased film strength may be readily measured by means of the Almen lubricating testing machine; a standard test method for lubricants required for lubrication under high pressure. Under this test the original oil withstood only 4000 pounds per square inch maximum load, while the improved lubricant withstood a maximum load of 8000 pounds per square inch. By employing larger percentages of the thioether than used in Example 3, the extreme pressure characteristics imparted to the oil are even more marked. Other thioethers may be used in lieu of the amyl de rivative and similar improvement obtained.

The above examples are but illustrative em mineral oils may be employed as a lubricating base in making lubricants of our improved type. The addition of the thioethers to these lubricating bases produces a likeimprovement in film strength and reduces their destructiveness toward the newer bearing metal alloys. When incorporating the thioethers in a grease composition or like thickened lubricant, mechanical agi-r tators rather than a current of air are employed to obtain uniform mixing and blending. That is, the thioether and grease may be compounded in the usual mixers such as blade mixers, equipped with heating jackets. However, in making such greases the thioether may advanta geously first be incorporated with the 011 base according to the procedure of Example 1 and then the metal soap or the thickening agents added to the improved oil, in the ordinary way, to produce the desired grease compositions. In other words, the improved mineral oils of the present invention may be used in lieu of the ordinary oils in making special lubricating compositions such as greases, etc. 7 v

The ethyl thioethers of ortho-nitrobenzene and other thioethers may be employed in lieu of the amyl thioether in the examples given ante. The amyl and like alkyl thiothers being particularly effective are ordinarily employed. With proper blending, good lubricants may be produced with all these thioethers compounded with various petroleum oils or mineral oil lubricants.

As stated ante, the incorporation of these thioethers with the lubricating base produces several improvements in the final lubricant without deleteriously affecting the desirable properties. While the exact reasons for the improvements obtained are not fully known, we are satisfied with observing and utilizing the actual improvements obtained by adding and incorporating these thioethers with. commercial lubricants.

The improved performance of lubricants secured in the presence of the newer alloy bearing metals by means of our present invention appears to result from the presence of an aryl thioether having a second substituent group in the ortho position to the said thioether group. In the present invention we claim specifically the use of materials wherein the substituent group ortho to the thioether group is a nitro group. In our copending application Serial No. 98,823, filed August 31, 1936 we describe and specifically claim materials wherein the substituent group is an amino group. Certain special advantages are secured with each of these types of materials.

What we claim is:

1. A method of lubricating bearing surfaces in I internal combustion engines when subjected to conditions of operation which comprises maintaining between bearing surfaces, one of which is an alloy formed chiefly of a metal of the class consisting of cadmium and copper, the film of a. lu-

bricating oil which initially produces an effective lubricating action but which would normally tend to corrode the aforesaid alloy, and maintaining the effectiveness of the lubricating oil by means of between102 per cent and 0.20 per cent by weight on the oil, of an ortho-nitro-phenyl alkyl thioether dissolved in such oil, said alkyl thioether having the following formula:

wherein R represents an alkyl group.

"2. A method of lubricating bearing surfaces in 17:52. COMPOSITIONS.

maintaining the effectiveness of the lubricatingoil by incorporating therein ortho-nitro phenyl amyl thioether in a small but suiiicient proportion substantially to retard the corrodon.

3. As a. new and improved lubricant capable of lubricating cadmium-silver and other special alloy bearings at high temperatures, pressures and speeds, without, corroding such alloy bearings, an improved motor oil comprising a mineral oil containing a minor amount of an alkyl thioether oi U! U00 HUIUI UllbU UUI b" 4. As an article of manuracture, a new and improved lubricant comprising a major proportion of a mineral lubricating oil containing a minor proportion of an ortho-nitrophenyl alkyl thioether dissolved therein, said thioether having the following formula:

wherein R represents'an alkyl group, and the amount of said thioether being suilicient to substantially improve the lubricating qualities of said lubricating oil.

5. The new and improved lubricant of claim 4 wherein said mineral lubricating oil contains from 0.02 to 2 per cent of said alkyl thioether oi ortho-nitrobenzene dissolved therein.

6. The new and improved lubricant of claim 4 wherein said thioether is-orthonitrophenyl am thioether.

7. The new and improved lubricant or claim 4 wherein said thioether is ortho-nitrophenyl ethyl thioether.

' TROY LEE CANTREIL.

JAMES O'I'HO TU.

IIUUIH: 

